Low-carbon solutions integration in power systems

Background and context

The European power system is on the critical path to meet the EU’s climate change and energy policy objectives. The power system is bound to be the place where low-carbon solutions and technologies - ranging from renewable energy generation sources to storage devices and electric vehicles - are interconnected and effectively interact with each other.

The challenge for the power system is to combine the sustainability-oriented policy targets with those linked to security of supply and competitiveness.

With the unprecedented deployment of low-carbon technologies for electricity generation, renewable energy generating units, storage solutions and electric mobility are expected to play an important role. Grid connected energy storage systems are regarded as promising solutions for providing ancillary services to electricity networks and to play an important role in the development of smart grids.

Our role

Against this background, we are monitoring the challenges for redesigning the European electricity systems and assessing options for the systemic integration of low-carbon solutions in the European electricity grids. More in detail, we are conducting targeted research on

renewable solutions integration into the power systems. We developed a methodology for supporting decision makers in identifying the most suitable spots for offshore wind farm connections.

storage solutions integration into new power system architectures. The main concerns for wide adoption are the overall cost, the limited number of charging cycles (or lifetime), the depth of discharge, the low energy density and the sustainability of materials used.

renewable, storage and EV solutions integration into new power system architectures.

2018 - Impact of PV self-consumption on distribution networks and regulatory implications

This paper performs a power flow-based quantitative assessment of such impact, using European representative distribution networks, and by discussing potential drawbacks which can be faced under different PV penetration scenarios and when different policies are put in place. Little attention has been paid so far to the effects of self-consumption policy design on the distribution networks, where most prosumers are connected. Results show that the size of the installations (driven by the self-consumption policy incentives) has a great impact on the voltage and thermal limit violations, which is sometimes even higher than the impact of the PV penetration level.

An in-depth discussion on the regulatory implications is also reported. The need to improve the tariff designs, so that they also reflect the extra costs in the distribution networks is discussed. Then, alternatives to avoid or defer network investments are proposed including the use of curtailment, the revision of current voltage limits, possibly too stringent in some countries, and the application of smart grid technologies. Finally, the key role of aggregator to provide flexibility services is identified.

2018 - Statistical characterisation of data from electric vehicle charging stations

This paper shows and analyses an important set of key figures (charge time, idle time, connected time, power, and energy) depending on driver's behaviour in the Netherlands.

Despite the many environmental benefits that a massive diffusion of electric vehicles (EVs) could bring to the urban mobility and to society as a whole, numerous are the challenges that this could pose to the electricity distribution grid, particularly to its operation and development. While uncoordinated management of EVs can lead to load imbalances, current or voltage variation excess and steep power requests, properly designed and well-coordinated integration approaches can in contrast provide flexibility, hence value, to the whole electrical system. Such step can be achieved only if real data are available and real drivers’ behaviours are identified.

This paper is based on a real dataset of 400,000 EV charging transactions. From these figures, it emerges a key role of the uncertainty of the relevant variables due to the drivers’ behaviour. This paper develops a Beta Mixture Model to represent these multi-modal probability distributions. Based on the emerged statistical facts, a number of results and suggestions are provided, in order to contribute to the important debate on the role of EVs to move to a fully decarbonised society.

2018 - Indicator-Based Methodology for Assessing EV Charging Infrastructure

This paper defines an assessment methodology, composed by eight indicators, allowing a comparison among EV public charging infrastructures. In order to support EV charging infrastructures design and operation, little attempt has been made to develop indicator-based methods characterising such networks across different regions. The proposed indicators capture the following: energy demand from EVs, energy use intensity, charger’s intensity distribution, the use time ratios, energy use ratios, the nearest neighbour distance between chargers and availability, the total service ratio, and the carbon intensity as an environmental impact indicator. We apply the methodology to a dataset from ElaadNL, a reference smart charging provider in The Netherlands, using open source geographic information system (GIS) and R software. The dataset reveals higher energy intensity in six urban areas and that 50% of energy supplied comes from 19.6% of chargers. Correlations of spatial density are strong and nearest neighbouring distances range from 1101 to 9462 m. Use time and energy use ratios are 11.21% and 3.56%. The average carbon intensity is 4.44 gCO_2eq/MJ. Finally, the indicators are used to assess the impact of relevant public policies on the EV charging infrastructure use and roll-out.

2018 - European representative electricity distribution networks

This paper presents a methodology to build representative distribution networks. In Europe there is a great diversity of distribution grids and distribution system operators (DSOs) and a consolidated and shared knowledge of their techno-economic features is missing. This fact represents a major hindrance for fully assessing the performances of distribution grids evolving towards Smart Grids embedding low-carbon technologies, digital services and emerging actors.

Starting with real data provided by 79 large European DSOs, several network indicators have been firstly devised to extract the required information. Later, based on these, nine representative networks have been built through the proposed methodology. The built networks are of two major types: large scale and feeder type networks. All the network models are made available to allow researchers to overcome confidentiality and intellectual property constraints and to perform in-depth analyses on distribution network models realistically mimicking portions of the EU distribution system. Finally current applications and future improvements are also discussed.

2017- Comparative Analysis of Online Estimation Algorithms for Battery Energy Storage Systems

This paper examines a combination of the adaptive unscented Kalman filter (AUKF) and the fast upper diagonal recursive least square (FUDRLS) for the parameter identification and the state of charge (SOC) estimation processes, respectively.

Reliability of battery energy storage systems (BESS) used for online applications, such as electric vehicles and smart grid, depends heavily on the accuracy and rapidness of the SOC estimation. Moreover, to achieve a robust SOC estimation, the battery model parameter identification process is of significant importance.

The analysis focuses on on-line applications and the results are compared with previous work. Experimental validation based on various setups and load conditions is conducted, whereas the advantages of the proposed combination are highlighted.

2017 - Automated energy management in distributed electricity systems: An EEPOS approach

This paper presents the EEPOS project’s approach to the automated management of flexible electrical loads in neighborhoods. The management goals are (i) maximum utilization of distributed generation in the local grid, (ii) peak load shaving/congestion management, and (iii) reduction of electricity distribution losses. Contribution to the power balance is considered by applying two-tariff pricing for electricity.

The presented approach to energy management is tested in a hypothetical sensitivity analysis of a distribution feeder with 10 households and 10 photovoltaic (PV) plants with an average daily consumption of electricity of 4.54 kWh per household and a peak PV panel output of 0.38 kW per plant. Energy management shows efficient performance at relatively low capacities of flexible load. At a flexible load capacity of 2.5% (of the average daily electricity consumption), PV generation surplus is compensated by 34–100% depending on solar irradiance. Peak load is reduced by 30% on average. The article also presents the load shifting effect on electricity distribution losses and electricity costs for the grid user.

2017 - Multi-criteria selection of offshore wind farms: Case study for the Baltic States

This paper (whose results can be also checked via this interactive map) presents a multi-criteria selection approach for offshore wind sites assessment. The proposed site selection framework takes into consideration the following aspects: electricity network security conditions, economic investments, operation costs and capacity performances relative to each potential site.

The selection decision is made through the Analytic Hierarchy Process, allowing end users to adjust the expected benefits according to their respective and global priorities. The proposed site selection framework is implemented as an interactive case study for three Baltic States in the 2020 time horizon, based on real data and extensive power network models, taking into consideration the foreseen upgrades and network reinforcements.

For each country the optimal offshore wind sites are assessed under multiple weight contribution scenarios, reflecting the characteristics of market design, regulatory aspects or renewable integration targets.

2016 - Support to renewable energy integration in Cyprus

This report describes the main results of the assistance project we carried out (along with DG SRSS and ENER) to support the Cyprus government to assess the current state of the transmission and distribution electricity systems and propose solutions for increasing the amount of Renewable Energy Sources generation that can be fed on the electricity system. More information of our support project to Cyprus is available here.

The main objective of the project was to help the Cyprus Government to establish a comprehensive medium- to long-term policy for the optimum penetration of renewable energy in the electricity system until 2030.

The project was divided in four activities which are tightly interlinked and correlated, spanning from system characterisation, to transmission/distribution simulation up to market analyses, with a view to perform an integrated assessment of the Cyprus electricity system (power infrastructure and markets).

2016 - Assessment framework for EV and PV synergies in emerging distribution systems

This paper proposes a conceptual architecture and an assessment framework to explore how high penetration scenarios of electric vehicles and intermittent renewable generation can complement each other in emerging distribution networks. We start from the identification of the smart grid functionalities to be implemented in a system with distributed power injections under the need to supervise and coordinate myriads of decentralized and interoperable energy sources and actors. Relying upon the proposed smart grid conceptual architecture, we develop an assessment framework to maximize the renewable electricity and electric vehicle penetration for given electricity and transport systems. The application of the proposed assessment framework to a realistic case study, representing the distribution and mobility systems of a typical mid-size Italian city, illustrates how some of the limitations and constraints of the current electricity network operation and design approaches can be addressed and overcome. We show how integration of substantial amounts of energy production and electric-based transport technologies can be achieved while improving the reliability and sustainability performances of the emerging power systems.

2016 - Smart grid energy storage controller for frequency regulation and peak shaving

This paper presents a model using MATLAB/Simulink, to demonstrate how a Vanadium Redox Flow Battery (VRFB) device can provide multi-ancillary services, focusing on frequency regulation and peak-shaving functions. Vanadium Redox Flow Batteries (VRFB) are a promising option to mitigate many of these shortcomings, and demonstration projects using this technology are being implemented both in Europe and in the USA. The study presents a storage system at a medium voltage substation and considers a small grid load profile, originating from a residential neighbourhood and fast charging stations demand. The model also includes an inverter controller that provides a net power output from the battery system, in order to offer both services simultaneously.

Simulation results show that the VRFB storage device can regulate frequency effectively due to its fast response time, while still performing peak-shaving services. VRFB potential in grid connected systems is discussed to increase awareness of decision makers, while identifying the main challenges for wider implementation of storage systems, particularly related to market structure and standardisation requirements.

2015 - Market Integration Scheme of a Multi-Terminal HVDC Grid in the North Seas

This paper examines the market integration of a centrally dispatched multi-terminalHVDC Grid based on droop control.

The development of a multi-terminal high voltage DC (HVDC) grid based on voltage source converter (VSC) technology has been envisaged as a key development for harnessing the vast offshore wind production potential of the North Seas.

Particular emphasis is given on the management of onshore imbalance volumes due to offshore wind power forecast errors. The economic importance of the control choices of the operator of such an active transmission grid is highlighted, and regulatory implications are briefly discussed.

The main contribution of the paper is the coherent development of a droop-controlled MT HVDC grid scheme that integrates optimal power flow (OPF) dispatch, and imbalance volume management.

2013 - Characterisation of electrical energy storage technologies

This paper provides a qualitative methodology to select the appropriate technology or mix of technologies for different applications. The multiple comparisons according to different characteristics distinguish this paper from others about energy storage systems. Firstly, the different technologies available for energy storage, as discussed in the literature, are described and compared.

The characteristics of the technologies are explained, including their current availability. In order to gain a better perspective, availability is cross-compared with maturity level. Moreover, information such as ratings, energy density, durability and costs is provided in table and graphic format for a straightforward comparison.

Additionally, the different electric grid applications of energy storage technologies are described and categorised. For each of the categories, we describe the available technologies, both mature and potential. Finally, methods for connecting storage technologies are discussed.

2010 - Load-following operating mode at Nuclear Power Plants and wind power variability

This report discusses the capability of nuclear power plants to modulate their power output to follow demand variations. Power ramp-up/down margins are indeed included as design rules in the European Utility Requirements (EUR rules) and should apply to the new builds in Europe. This report estimates also the load following operating margins in combination with wind farm variable outputs, drawing on experience gained in the wind turbines sector in Europe (Scandinavia) and the US. This allows to estimate the compatibility of wind and nuclear generating units in a selected geographic area. A central point is to study the impact on the nuclear generating plant's economical profitability, due to possible higher operation and maintenance costs, of the plant's contribution to grid regulation. As electricity price and cost components are not fully disclosed in a liberalised market framework, this study is based on expert judgement and aggregated data from an IAEA database collecting yearly average loss of production of nuclear power plants worldwide. The study shows that a 2% increase in the operation and maintenance O&M costs would allow a nuclear power plant be eligible for modulation (load-following operating mode) and thus benefit from much higher electricity prices than in the base-load situation.

2010 - Improving network controllability by FACTS and HVDC transmission systems

This report aims at describing the main features of two key families of advanced power technologies, which may play a crucial role in the further development of the European transmission system: Flexible Alternating Current Transmission System (FACTS) and High Voltage Direct Current (HVDC) transmission. These power electronics-based devices offer the possibility to increase transmission network capacity as well as flexibility and generally enhance system reliability, security, and controllability with a limited environmental impact. FACTS and HVDC may provide transmission planners with effective solutions to several problems they encounter nowadays in planning their grids. After illustrating the technical characteristics of the different FACTS and HVDC technologies, crucial economic and environmental figures are provided. These elements are needed for a techno-economic and also environmental assessment of the impact of such devices on the system. Also planning guidelines for general and some specific application cases are described in this report. The final goal is to provide the European TSOs with the key elements of FACTS and HVDC and with guidelines to support their decision-making to select the most sound expansion alternative, while including FACTS and HVDC among the possible reinforcement options of modern transmission planning processes.

2009 - Methods for transmission planning and grid connection of wind power plants

This report, after offering an overview of the regulatory and market framework affecting the EU transmission system at large, and the renewable energy deployment in particular,

- lists and compares the technical requirements and the charging policy for the connection of new power plants to the European transmission grid, specifically focusing on wind generation (whenever related technical specifications are applied);

- provides an updated picture of the European transmission network planning challenges and practices, also by devoting special attention to the interactions between system development and (onshore/offshore) wind deployment.

2008 - Distributed Power Generation in Europe: Technical Issues for Further Integration

This report focuses on the potential role of Distributed Generation (DG) in a European perspective. More specifically, this work aims to assess the technical issues and developments related to DG technologies and their integration into the European power systems. As a starting point the concept of Distributed Generation is characterised for the purpose of the study. Distributed Generation, defined as an electric power source connected to the distribution network, serving a customer on-site or providing network support, may offer various benefits to the European electric power systems. DG technologies may consist of small/medium size, modular energy conversion units, which are generally located close to end users and transform primary energy resources into electricity and eventually heat. There are, however, major issues concerning the integration of DG technology into the distribution networks. In fact, the existing distribution networks were not generally designed to operate in presence of DG technologies. Consequently, a sustained increase in the deployment of DG resources may imply several changes in the electric power system architecture in the near future. The present Report on Distributed Generation in Europe, after an overview of the basic elements of electric power systems, introduces the proposed definition and main features of DG. Then, it reviews the state-of-the-art of DG technologies as well as focuses on current DG grid integration issues. Technical solutions towards DG integration in Europe and developments concerning the future distribution systems are also addressed in the study.